Pollen development in ashh2 and pASHH2:GUS expression in anther development.
(A) Average number of pollen per anther (nwt = 4, nashh2>8) in wt and ashh2 mutant lines. Standard deviations are shown. (B) Light- and fluorescent micrographs of ashh2-1 anthers and germinating pollen tubes. (i) Four long stamina from ashh2-1 from a flower just before abscission. All anthers are delayed in dehiscence. Note different numbers of pollen (p) in each locule and absence of normal locule development (arrows). (ii) Mature ashh2-1 anther with released pollen in the trinucleate stage (boxed area). Inset is a magnification of the boxed area, (s) sperm cell, (v) vegetative cell. (iii) Pollen tube germination on the papillae in ashh2-1. (p) pollen, (pt) pollen tube. (C) Stage 7 flower of pASHH2:GUS plant. No GUS expression was seen in the developing floral organs but only in the pedicel. s – sepal; g – gynoecium; pp – petal primordium; sp – stamen primordium. (D) Stage 9 to 11 flowers showing increasing GUS expression post meiosis. The boxed insert shows that no GUS expression was detected in tetrads. s – sepal; g – gynoecium; a – anther. (E) Stage 12 flower with mature anthers with GUS expression in anthers (a), as well as the gynoecium (g) and mid veins of petals (p) and sepals (s). (F) Anther of stage 12 flower showing GUS expression both in the tapetal cell layer (t) and the mature microspores (ms), but not in the anther filaments (f). (G) Detail of GUS expression in floral stage 12 anther demonstrate specific expression in tapetum (t) and microspores (ms), but not in the surrounding endothecium (en) and epidermis (e) cell layers. (H) Scanning electron micrographs of wt pollen (i) with a sexine layer (ii) with regular ridges (muri – m) and spaces (lumina – l). (I) Scanning electron micrographs of ashh2-1 pollen grains (i, ii) and exine layers with filled muris (iii), and in severe cases visible nexine layer (n) and bacula (b) due to absent tectum layer (iv).